Field of the Invention
The present disclosure relates to a switchable type touch display device, and more particularly, to a switchable type touch display device where a thickness decreases and fabrication cost is reduced by forming an electrode for touch on a polarization control panel and a method of driving the same.
Discussion of the Related Art
Recently, a liquid crystal lens where a liquid crystal layer functions as a lens by using an optical anisotropic property of a liquid crystal molecule has been suggested, and a switchable type display device where a two-dimensional (2D) image or a three-dimensional (3D) image is selectively displayed by using a liquid crystal lens has been suggested. The switchable type display device includes a display panel, a polarization control panel and a lens panel.
In addition, a touch display device (or a touch screen) which is used as an output means for displaying an image and as an input means for receiving an order of a user by touching a portion of the displayed image, has been spotlighted. The touch display device includes a display panel and a touch panel.
Further, a switchable type touch display device which selectively displays a 2D image or a 3D image and receives an order of a user by applying the touch panel to the switchable type display device has been developed. The switchable type touch display device will be illustrated with reference to drawings.
FIGS. 1A and 1B are cross-sectional views showing optical paths of a switchable type touch display device in a 2D mode and a 3D mode, respectively, according to the related art.
In FIGS. 1A and 1B, a switchable type touch display device 10 includes a display panel 20, a polarization control panel 30, a lens panel 50 and a touch panel 60. The display panel 20 displays an image using a plurality of pixels including first to third pixels P1 to P3. The polarization control panel 30 includes first and second polarization control substrates 32 and 34 facing and spaced apart from each other and a polarization control liquid crystal layer 36 interposed between the first and second polarization control substrates 32 and 34. First and second polarization control electrodes 38 and 40 are formed on inner surfaces of the first and second polarization control substrates 32 and 34, respectively.
The lens panel 50 includes first and second lens substrates 52 and 54 facing each other and a lens liquid crystal layer 56 interposed between the first and second lens substrates 52 and 54. A plurality of concave portions each having a half cylindrical shape are formed on an inner surface of the second lens substrate 54 and are filled with the lens liquid crystal layer 56. In addition, a plurality of liquid crystal molecules 56a of the lens liquid crystal layer 56 are arranged such that a long axis of the liquid crystal molecule 56a is parallel to the plane of the paper (i.e., the cross-sectional plane). The liquid crystal molecule 56a has a birefringence property such that the liquid crystal molecule 56a has an ordinary refractive index no and an extraordinary refractive index ne according to a propagation direction of light. Further, the second lens substrate 54 includes a material having the ordinary refractive index no of the liquid crystal molecule 56a. 
The touch panel 60 includes a touch substrate 62 and transmission and reception electrodes 64 and 66 formed on both surfaces, respectively, of the touch substrate 62. The touch panel 60 detects a touch position from a change in capacitance between the transmission and reception electrodes 64 and 66 generated according to a touch or not in a state where voltages are applied to the transmission and reception electrodes 64 and 66.
The switchable type touch display device 10 selectively displays a 2D image or a 3D image according to a polarization state of the polarization control panel 30. First to third lights L1 to L3 emitted from the first to third pixels P1 to P3, respectively, have a first polarization state PS1 where a polarization axis is parallel to the plane of the paper.
In a 2D mode where the 2D image is displayed as shown in FIG. 1A, since the first and second polarization control electrodes 38 and 40 have no voltage difference, an electric field is not generated between the first and second polarization control electrodes 38 and 40 of the polarization control panel 30. As a result, while the first to third lights L1 to L3 pass through the polarization control panel 30, the first to third lights L1 to L3 have a retardation of λ/2 (half wave). Accordingly, after the first to third lights L1 to L3 pass through the polarization control panel 30, the first to third lights L1 to L3 have a second polarization state SP2 where a polarization axis is perpendicular to the plane of the paper and enter the lens panel 50.
Since the liquid crystal molecule 56a of the lens liquid crystal layer 56 has a long axis parallel to the plane of the paper, the first to third lights L1 to L3 of the second polarization state PS2 feel that the lens liquid crystal layer 56 has the ordinary refractive index no. As a result, the first to third lights L1 to L3 of the second polarization state PS2 feel no refractive index difference at an interface between the lens liquid crystal layer 56 and the second lens substrate 54. Accordingly, the first to third lights L1 to L3 of the second polarization state PS2 straightly pass through the lens panel 50 without refraction so that the switchable touch display device 10 can display the 2D image.
In a 3D mode where the 3D image is displayed as shown in FIG. 1B, since the first and second polarization control electrodes 38 and 40 have a voltage difference, an electric field is generated between the first and second polarization control electrodes 38 and 40 of the polarization control panel 30. As a result, while the first to third lights L1 to L3 pass through the polarization control panel 30, the first to third lights L1 to L3 have no retardation. Accordingly, after the first to third lights L1 to L3 pass through the polarization control panel 30, the first to third lights L1 to L3 still have the first polarization state SP1 and enter the lens panel 50.
The first to third lights L1 to L3 of the first polarization state PS1 feel that the lens liquid crystal layer 56 has the extraordinary refractive index ne. As a result, the first to third lights L1 to L3 of the first polarization state PS1 feel a refractive index difference at the interface between the lens liquid crystal layer 56 and the second lens substrate 54. Accordingly, the first to third lights L1 to L3 of the first polarization state PS1 are refracted while passing through the lens panel 50 so that the switchable touch display device 10 can display the 3D image.
In the switchable type touch display device according to the related art, since the touch panel for detecting touch as well as the polarization control panel for switching are required, a total thickness of the switchable type touch display device increases and fabrication cost increases according to complicated fabrication process. In addition, since there exists a limit in capacity and life time of a battery due to increase of power consumption for driving the display panel, the polarization control panel and the touch panel, it is difficult to apply the switchable type touch display device to a mobile device. Further, it is difficult to apply the switchable type touch display device to a partial 2D/3D display where a part such as an icon and a text is displayed as the 2D image and the other part such as a moving picture is displayed as the 3D image.